排序方式： 共有38条查询结果，搜索用时 312 毫秒
31.
Toshihiro Yoshimura Rei Nakashima Atsushi Suzuki Noriko Tomioka Hodaka Kawahata 《Journal of Paleolimnology》2010,43(3):437-448
We present oxygen and carbon isotope ratios and the morphological structure of the cultured freshwater pearl mussel (Hyriopsis sp., Unionidae) shell and pearl. The number of first-order fluctuations of δ18O of the outer shell layer along the maximum growth axis was consistent with the number of cultured years. The dominant factor
controlling annual δ18O fluctuations was water temperature with a minor contribution from the variation in δ18O of ambient water, especially during the rainy season. The δ13C values were approximately constant throughout the life of the mussel, suggesting that the contributions of body size to
δ13C of the shell were minor. We observed nine distinct disturbance rings on the outer surface of the shell. Five rings coincided
with the five winter peaks of the δ18O profile, indicating winter growth cessation below approximately 10°C, probably because of either inactive growth at low
water temperatures or reproduction. Summer disturbance rings were not observed in all years. Moreover, some summer rings showed
discontinuity in the inner structure. These findings suggest that summer growth cessation may be caused by occasional events
such as heavy rains, as the decrease of dissolved oxygen concentration. The δ18O profile and shell structures indicated that shell aragonite was precipitated at close to equilibrium conditions with respect
to the oxygen isotope composition of the ambient water. Hyriopsis sp. shells can potentially be used for reconstruction of past hydrologic conditions. The δ18O of a pearl indicated that calcification occurred over a temperature range of at least 13–23°C. The optimal temperature for
pearl calcification in this species is lower than that for marine pearl calcification. 相似文献
32.
Development of new sensor systems for continuous bedload monitoring using a submerged load‐cell system (SLS) 
下载免费PDF全文
下载免费PDF全文 Takahiro Itoh Takahiko Nagayama Rei Utsunomiya Masaharu Fujita Daizo Tsutsumi Shusuke Miyata Takahisa Mizuyama 《地球表面变化过程与地形》2018,43(8):1689-1700
It is important to evaluate bedload discharge and temporal changes of the bed surface, and bed deformation can be estimated during floods if the bedload discharge is properly evaluated in an arbitrary cross‐section. With the exception of grain size and its distribution within the bedload, bedload discharge has been measured using both direct and indirect methods. Bedload slot is a direct method but cannot be used to measure bedload during a flood because of volume limitations. Indirect methods require correlation between the signals and sediment volume measured using another method. In the present study, a small, automatically recording bedload sensor with an iron plate and a pair of load cells is developed in order to evaluate not only large particles but also sand particles as bedload. Bedload mass is calculated by integrating with respect to both the velocity of sediment particles and the averaged particle weight as measured by a pair of load cells, and, as an example, the velocity is estimated by the cross‐correlation function of weights measured by load cells. The applicability of the proposed sensor is discussed based on the results of flume tests in the laboratory (2014) and the observation flume of the Hodaka Sedimentation Observatory of Kyoto University in Japan (2015). The system was installed in the observation flume in November of 2012, and flume data were obtained using natural sediment particles. In particular, it was difficult to estimate the velocity of averaged bedload particles, and it was better to apply a cross‐correlation function in the laboratory tests. However, it appears that the previous estimation can estimate these velocities in the observation flume using a connecting tube and submerged load‐cell systems. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
33.
Rei Sonobe Yuki Yamaya Hiroshi Tani Xiufeng Wang Nobuyuki Kobayashi Kan-ichiro Mochizuki 《国际地球制图》2019,34(8):839-855
Developing techniques are required to generate agricultural land cover maps to monitor agricultural fields. Landsat 8 Operational Land Imager (OLI) offers reflectance data over the visible to shortwave-infrared range. OLI offers several advantages, such as adequate spatial and spectral resolution, and 16 day repeat coverage, furthermore, spectral indices derived from Landsat 8 OLI possess great potential for evaluating the status of vegetation. Additionally, classification algorithms are essential for generating accurate maps. Recently, multi-Grained Cascade Forest, which is also called deep forest, was proposed, and it was shown to give highly competitive performance for classification. However, the ability of this algorithm to generate crop maps with satellite data had not yet been evaluated. In this study, the reflectance at 7 bands and 57 spectral indices calculated from Landsat 8 OLI data were evaluated for its potential for crop type identification. 相似文献
34.
35.
36.
Treadaway Victoria Atlas Elliot Schauffler Sue Navarro Maria Ueyama Rei Pfister Leonhard Thornberry Troy Rollins Andrew Elkins James Moore Fred Rosenlof Karen 《Journal of Atmospheric Chemistry》2022,79(2):81-100
Journal of Atmospheric Chemistry - Rapid transport by deep convection is an important mechanism for delivering surface emissions of reactive halocarbons and other trace species to the tropical... 相似文献
37.
38.
Seafloor hydrothermal alteration at an Archaean mid-ocean ridge 总被引：2，自引：0，他引：2
A hydrothermally metamorphosed/altered greenstone complex capped by bedded cherts exposed in the North Pole, Pilbara Carton, Western Australia, is interpreted as an accretionary complex. It is distinctive in being characterised by both duplex structure and an oceanic crust stratigraphy. This complex is shown to represent an Archaean upper oceanic crust with a mid‐ocean ridge hydrothermal metamorphism that increases in grade stratigraphically downward. Three mineral zones have been defined; Zone A of the zeolite facies, the prehnite‐pumpellyite facies or the lower‐greenschist facies at high‐XCO2 condition, Zone B of the greenschist facies, and Zone C of the greenschist/amphibolite transition facies. In Zone A metabasites, Ca‐Al silicates including Ca‐zeolites, prehnite and pumpellyite are absent and epidote/clinozoisite is extremely rare. Instead, abundant carbonates are present with chlorite suggesting high‐XCO2 composition in the fluid. On the other hand, in Zones B and C metabasites, where Ca‐amphibole + epidote/clinozoisite + chlorite + Ca‐Na plagioclase are the dominant assemblages, carbonate is not identified. The metamorphic conditions boundary of Zones B/C were estimated to be about 350 °C at a pressure of <0.5 kbar. Fluid compositions coexisting with Archaean greenstones at the transition between Zones B and C were estimated by thermodynamic calculation in the CaFMASCH system (T = 350–370 °C, P = 150–1000 bar) at XCO2 of 0.012–0.140, such values are higher than present‐day vent fluids collected near mid‐ocean ridges with low‐XCO2 values, up to 0.005. The Archaean seawater depth at the mid‐ocean ridge was estimated to be 1600 m at XCO2 = 0.06 using a depth‐to‐boiling point curve for a fluid. The carbonation due to high‐XCO2 hydrothermal fluids occurred near the ridge‐axis before or was coincident with ridge metamorphism. 相似文献